416 stainless steel is a free-machining martensitic stainless steel with 12-13% chromium that can be hardened by heat treatment to higher strength and hardness levels. In the annealed condition, it has better machining properties than typical austenitic stainless steels like 304 & 316.
416 is highly resistant to typical atmospheric conditions with maximum corrosion resistance obtained by hardening and polishing. Typically free-machining grades are not welded due to problems stemming from the free-machining additives. If welded, 416 stainless must be annealed after welding at approximately 1450°F to improve ductility and corrosion resistance.